Science: Microbial Kill

The once-predominant oxidizing biocides (chlorine and bromine) are relatively ineffective antimicrobials at alkaline pH. Most non-oxidizers lack the penetrating ability to control the biological growth within a biofilm, and lack the ability to remove an established biofilm.

Chlorine dioxide is effective at alkaline pH, and has excellent disinfection properties for both planktonic and sessile bacteria; it also is singularly effective at destroying established biofilm.

Some of the advantages of chlorine dioxide include: (a) chlorine dioxide will eliminate blue-green algae (chlorine cannot), (b) chlorine dioxide does not chlorinate organic molecules (no chlorophenols or trihalomethanes) (c) chlorine dioxide’s biocidal activity is constant over a wide pH range (d) chlorine dioxide is a wide spectrum biocide, eliminates bacteria, fungi and viruses (e) there is no noticeable delignification of cooling tower wood.

Chlorine dioxide rapidly inactivates bacteria, viruses parasites such as Giardia and to some extent, even the highly resistant encysted parasite Cryptosporidium. Chlorine dioxide’s combination of power and selectivity enable it to penetrate bio films and destroy the resident microorganisms.

The inactivation of bacteria by chlorine dioxide has been attributed to the selective oxidation of nitrogen-nitrogen bonds in amino acids—hierarchically, tyrosine, tryptophan, cystine, cysteine — resulting in disruption of protein synthesis. In the case of viruses, chlorine dioxide is believed to denature the outer protein layers. Chlorine dioxide appears not to attack DNA or RNA, or to cause nucleic-acid leakage.